Fix certificate View link (wrong /study/certificate URL), certificates in My Account, name on certificate; v2.10.10

- Certificate URLs in the account overview and the issuance email pointed at /study/certificate/:token,
  which the router treated as a lesson page; now /certificate/:token (old links redirect)
- My Account Certificates card lists every enrolled study: progress, Generate, View, Copy link, Download PNG, Share
- Certificate canvas used a non-existent /api/study-account route and always printed 'Student'; now reads the account name
- Panel no longer collapses after generating

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

server/routes/study-account.js

@@ -225,7 +225,7 @@ export function register(app) {
         studySlug: c.studySlug,
         studyTitle: c.studyTitle,
         issuedAt: c.issuedAt,
-        url: buildAbsoluteUrl(baseUrl, `/study/certificate/${c.token}`),
+        url: buildAbsoluteUrl(baseUrl, `/certificate/${c.token}`),
       }))
 
     res.json({